1. Field of the Invention
The present invention relates to a drive mechanism for use in an automotive side-view mirror assembly of a motor-driven folding type, and more particularly to a drive mechanism destined for use in such a mirror assembly to pivot in relation to the mirror base which is to be fixed to a car body the mirror housing supporting the mirror in such a manner that the latter can be turned vertically and horizontally, thereby folding the mirror to the folded position or returning to the normal position.
2. Prior Art
The drive mechanism for an automotive side-view mirror assembly of a motor-driven folding type comprises an electric motor fixed in a mirror housing, a speed reducer including reduction gears to reduce the revolution of the motor, and a device to convert the revolution output of the speed reducer into a revolution of the mirror housing itself. Normally, remote-controlled mirror assemblies have disposed in the mirror housing thereof a drive unit to turn the mirror itself vertically and horizontally. Thus, the drive unit comprising a drive motor, speed reducer and converter is to be disposed in a limited space in the mirror housing.
The speed reducer forming a part of the drive unit used in such automotive side-view mirror of a motor-driven folding type is a relatively compact, lightweight one which uses planet gears in order to achieve a high reduction ratio. However, a single-stage speed reduction by a single planet gear cannot provide a desired reduction ratio. Normally, a multi-stage planet gear unit is used in the form of a plurality of planetary gear units housed in an elongated cylindrical casing having common ring gears formed on the inner wall thereof. More particularly, the required sizes of the ring gears, sun gears, planet gears and planet carriers in the multi-stage planetary gear unit disposed in the limited space in the mirror housing are extremely small. Therefore, the manual assembling of the planetary gear units one by one into the elongated casing is very complicated and requires at the present great skill, much time and labor.